High molecular weight factor in FCS inhibits Helicobacter pylori VacA-binding to its receptor, RPTPbeta, on AZ-521.

VacA, a secretory product of Helicobacter pylori, binds to its cell surface receptor, receptor tyrosine phosphatase (RPTP) beta, leading to cytoplasmic vacuolization of gastric epithelial AZ-521 cells. VacA binding to the cell surface and VacA-dependent vacuolization were inhibited by cell culture media containing fetal calf serum (FCS). The high molecular weight fraction of FCS isolated by Superose 12 gel filtration chromatography inhibited VacA binding, whereas only weak effects were observed with other fractions. These data show that the high molecular weight fraction of FCS inhibits VacA action though its ability to block toxin binding to its receptor, RPTPbeta, on AZ-521 cells.